1. Field of the Invention
The present invention relates in general to deployable cables for use in seismic surveying and comprising discontinuities as for example transducers/sensors for sensing of received acoustic signals at subsea locations resulting from at least one generated seismic signal. More particularly, the invention relates to a system and a method for storing, transporting and/or handling seismic cable(s) incorporating a number of seismic stations or other discontinuities for use in seismic surveying at offshore locations. Operations, related to deployment and/or retrieval of such cables, are generally aimed at placing a seismic cable on the sea bottom, normally in a trench, under different weather conditions and with a failure rate as low as possible.
2. Description of the Related Art
Storing, transportation, deployment and/or retrieval of subsea cables is/are now a common procedure performed by a number of operators.
Typically, the subsea cables are very long and consist of a number of discontinuities, e.g., regenerators. When repeaters are included along the cable, such repeaters usually require special handling, such as e.g., hand carrying, in the deployment apparatus onboard a vessel, in order to ensure that no damage is made to the repeaters.
Published US Patent Application No. 2007/0248417 A1, to Berg, teaches a method and system for use in storage, deployment or retrieval of a seismic cable comprising a number of seismic stations.
Published US Patent Application No. 2004/0065443 A1, to Berg et al., describes an apparatus and method for transporting, deploying and retrieving an array of a plurality of nodes interconnected by sections of a cable. An apparatus and a method for transporting, deploying and retrieving a preassembled fiber optic in-well seismic array having a plurality of fiber optic sensors, clamp mechanisms and sections of cables between sensors is also described.
As described in published US Patent Application No. 2004/0065443 A1, some difficulties are encountered when sections of the seismic cable and its nodes are wound on to or unwound from a cable drum or other carrying device, due to the size, shape and construction of the nodes. Typically, the nodes constitute bulges on the cable, and the nodes are typically less flexible than the other sections of the seismic cable.
One drawback of the present solutions for seismic cable storage, deployment and retrieval is that the volume of a seismic cable storage or transportation system or device is not utilized very efficiently.
Another drawback of the present solutions for seismic cable storage, deployment and retrieval is that the transportation of the drum(s) with spooled or coiled cable requires special solutions because of the size.
Yet another drawback of the present solutions for seismic cable storage, deployment and retrieval is that a heavy and long cable has a tendency to move and unwind from the drum. In addition, if there are a number of seismic stations on a seismic cable, the cable may easily become trapped between other layers of cable or behind seismic stations and an entangled cable may result in kinks or even eventual breakage of the cable when unspooled.
Storing, transportation, deployment and retrieval of seismic cables which include a large number of sensor points or sensor stations with interconnecting cable is presently a challenge for most seismic cable operators or companies.
There exists a need for an improved storage device or system for use in cable storage, deployment and retrieval which may facilitate more efficient and predictable storage, deployment and retrieval of seismic cables, and a method which enables improved functionality while reducing the above mentioned drawbacks of the present solutions.